A navigation system performs travel guidance for enabling a user to easily and quickly reach the selected destination. A typical example is a vehicle navigation system where a user drives a car having a vehicle navigation system. Such a navigation system detects the position of the user or user's vehicle, reads out map data pertaining to an area at the current vehicle position from a data storage medium. Alternatively, such map data can be provided to the user from a remote server through a communication network such as Internet.
When a destination is set, the navigation system starts a route guidance function for setting a guided route from the start point to the destination. During the route guidance, the navigation system reads the nodes data from the data storage medium such as DVD and successively stores the nodes data of road segments constituting the guided route in a memory. In the actual traveling, the node series stored in the memory is searched for a portion of the guided route to be displayed in a map display area of the monitor screen, and the portion of the guided route is highlighted so as to be discriminable from other routes. When the vehicle is within a predetermined distance of an intersection it is approaching, a highlighted intersection diagram with an arrow indicating the direction to turn at the intersection is displayed to inform the user of the appropriate road or direction at the intersection.
FIGS. 1A–1H show an example of overall procedure and screen display involved in the navigation system. FIG. 1A shows an example of locator map screen of the navigation system when the destination is not specified. Typically, the navigation system displays a street on which the vehicle (current vehicle position VP) is running on a map image and a name of the street. Other information such as a north pointer NP, a map scale and a current time may also be illustrated on the display screen.
FIGS. 1B–1F show an example of process for specifying a destination in the navigation system. When selecting a “Destination” menu on a main menu screen (not shown), the navigation system displays an “Find Destination By” screen as shown in FIG. 1B for specifying an input method for selecting the destination. The “Find Destination By” screen lists various methods for selecting the destination. The methods include “Address” for specifying the city and address of the destination, “Intersection” for specifying the names of two streets which intersect with one another, and “Point of Interest” (POI) for selecting the programmed destination based on the name, category or telephone number. Other methods in the “Find Destination By” screen include “Recent Route” for specifying the destination based on the recent history of destinations saved in the navigation system, “Address Book” for selecting the address of the destination out of the prescribed address list stored in the system, and “Today's Plan” for selecting two or more destinations.
When selecting, for example, the “Point of Interest” method in FIG. 1B, the navigation system displays selection methods of point of interest (POI) either by “Place Name” or “Place Type” in FIG. 1C. The “Place Name” is to specify a name of POI, and the “Place Type” is to specify a category of POI. If the “Place Type” is selected in FIG. 1C, the navigation system shows an “Select Category” screen such as shown in FIG. 1D.
Suppose the user selects “Restaurant”, the navigation system retrieves the POIs in the selected category, restaurant, in this case, as shown in FIG. 1E. Typically, names of POIs (restaurants) will be listed in the order of distance from the user (ex. current vehicle position). If the user selects a particular restaurant from the list, the navigation system displays a “Confirm Route” screen such as shown in FIG. 1F. In this example, the “Confirm Route” screen lists the name, address and phone number of the destination (POI specified by the user). If this is the correct destination, the user enters an “OK to Proceed” key to proceed to the next procedure.
In FIG. 1G, the navigation system calculates and determines a route to the destination, i.e., the selected POI. The navigation system determines a route to the destination based on, for example, the shortest way to reach the destination, the route using many free ways as possible or the route without using toll road, and the like. In this example, the navigation system displays a progress scale of the calculation of the route.
After determining the guided route, the navigation system starts the route guidance as shown in FIG. 1H to guide the user along the calculated route to the destination. Typically, the navigation system shows the intersection which is highlighted to show the next turn and a direction of the turn. Such route guidance by the navigation system is also accompanied by voice instructions.
The foregoing is a typical example of using the “Point of Interest (POI)” input method of the navigation system. Because the recent storage medium provides a large volume of POI data, this input method can be used in various applications. For example, suppose a user is driving a car for a relatively long trip and the final destination is already specified in the vehicle navigation system, i.e., a calculated route to the destination is established. During the trip to the destination, the user wants to stop by various places such as a gas station, restaurant, shopping mall, etc., along the calculated route. Alternatively, the user may simply want to enjoy seeing various places surrounding the calculated route to the destination with use of the list of POI names on the monitor screen.
Thus, there is a need of a function in a navigation system for searching POIs along the calculated route to the destination during the trip. It is preferable to sort the searched POIs by distance ranges on the display. There is also a need of a display method for listing the POIs along the calculated route in the order that the user actually see them when he is moving. Such a situation is shown in FIGS. 2A–2E where a user is travelling to the destination (Dest) while the navigation system is listing POIs of selected category such as “Restaurant”. FIG. 2A shows an example of calculated (guided) route to the destination where the user (vehicle position VP) is at a position A. Typically, the user selects to list the POIs in the order of distance from the user's current position as shown in FIG. 2B. FIG. 2C shows an example of listing the POIs (restaurants) in the order of distance.
When sorting POIs by distance, generally, the distance for each POI is measured along the drive length on the road rather than the straight-line length. Thus, in the example of FIG. 2A, the POI names will be listed in the order of “Pizza Hut”, “Hard Rock Cafe”, “Inka”, “Genkai” and “Sushi Boy” as shown in FIG. 2C. The order of POIs in the list of FIG. 2C may not be the order that the user actually sees while driving the calculated route.
For example, at the position A, “Hard Rock Cafe” looks closer to the user than “Pizza Hut”. This is because the straight-line distance of “Hard Rock Cafe” is smaller than that of “Pizza Hut”. However, the actual drive length to “Hard Rock Cafe” is longer than that of “Pizza Hut” because of the particular road situation. Thus, the POI list of FIG. 2C correctly lists “Pizza Hut” prior to “Hard Rock Cafe”. In this situation, however, it is preferable that “Hard Rock Cafe” is listed prior to “Pizza Hut” because there is not a significant difference in the total drive length to either POI, and the user sees “Hard Rock Cafe” closer than “Pizza Hut”.
Further, at the position A, the user sees and feels that “Genkai” is closer to the user than “Inka” although the actual length along the road to “Genkai” is much longer than that of “Inka”. Thus, at the position A, if the selected category of POIs (ex., restaurants) are sorted by distance (FIG. 2D), the order shown in FIG. 2E may match what the user actually sees rather than the order of FIG. 2C. However, because there is a significant difference in the actual drive length between “Inka” and “Genkai” it may not be appropriate to list the order of these POIs in a manner too inconsistent to the actual drive length. Further, at the position of B, the order of actual distance (road length) and the order of actual view (straight-line length) between “Inka” and “Genkai” are the same.
In other words, the order of POIs that the user can actually see varies dynamically depending the position and the surrounding conditions of the calculated route. Further, in such a situation of FIG. 2A, a POI which is substantially deviated from the route such as “IHOC” should be excluded from the POI list. Thus, there is a need of a display method for a navigation system that can search POIs along the route to the destination within a predetermined transversal range and list the POIs in an order that a user actually see while taking consideration of balance with actual drive lengths to the POIs.